1. Field of the Invention
This invention relates to the elevator mechanisms utilized on self-loading elevator type scrapers.
Such mechanisms generally comprise a substantial frame structure which supports the sprockets and idlers over which are trained two endless chains. Flights or slats are connected between the chains, and driving means such as a hydraulic motor, electric motor, a separate engine or a power takeoff from the main engine of the vehicle is provided to operate the endless chains.
During a loading operation, the lower end of the elevator is located adjacent the cutting edge of the scraper which is cutting through the soil. The flights engage the soil in sequence as the chains rotate, loosening the soil, after which the flights then assist in pushing the loosened soil back into the scraper bowl as the scraper moves forward.
2. Description of the Prior Art
Heretofore, elevators for elevating scrapers have been driven from the top, that is, the endless chains are trained over driving sprockets and the driving sprockets are located at the upper or remote end of the elevator mechanism from the ground.
Usually in prior elevators, the endless chains are trained over idlers or idler rollers which do not have teeth, which are located at the bottom of the elevator, and it is this bottom end of the elevator which is moved near to the cutting edge during a loading operation in order to cut into the soil and move it into the bowl in conjunction with the forward movement of the scraper.
In the operation of such an elevator mechanism, there are two principal forces which act upon the chains and associated parts. One is a shock load or transient force which occurs each time a flight strikes the earth. The other is a relatively steady force caused by the flights dragging dirt back into the scraper bowl, the magnitude of the latter force increasing as the bowl fills with dirt, making it necessary to move the dirt farther up and back to get it on top of the dirt already in the bowl. Both of these mentioned forces are subject to variations, but it is the transient or shock forces which cause the more severe stresses and are more deleterious to the elevator mechanism and which cause the most wear, particularly to the chains. Such forces also make it necessary to have a relatively heavy and strong frame structure when a conventional elevator drive is used, to aid in withstanding the transient forces and also aid in preventing wear of parts of the elevator mechanism such as the chains by avoiding undue distortion during operation.